STL Volume & Weight Calculator

How to calculate the volume of an STL file

The volume of an STL file is the amount of 3D space enclosed by its triangle mesh — the figure that determines how much filament, resin or metal powder a print will consume, and therefore its cost and weight. Because an STL stores a model as a closed surface of triangles, you cannot simply multiply length × width × height (that gives the bounding box, not the part). The correct method sums the signed volume of a tetrahedron formed by each triangle and the origin; iamRapid's calculator does exactly this on the welded mesh, the same approach used by professional slicers.

To calculate STL volume online with this tool: upload your STL or OBJ file using the dropzone above, and the engine instantly reports the volume in cubic centimetres (cm³) and cubic millimetres (mm³), the surface area, the bounding-box dimensions and an estimated material weight. There is nothing to install, no account, and your model never leaves your browser.

Volume, density and weight — the definitions

• Volume — the enclosed 3D space of the model, measured here in cm³ (cubic centimetres, also written “cc”) and mm³. 1 cm³ = 1000 mm³.
• Surface area — the total area of all triangles in the mesh, in cm² / mm²; useful for estimating coating, support contact and post-processing.
• Bounding box — the smallest X × Y × Z box that contains the part, used to check it fits a printer's build volume.
• Density — the mass of a material per unit volume, in g/cm³. For example PLA is about 1.24 g/cm³ and aluminium AlSi10Mg about 2.67 g/cm³.
• Weight — estimated as weight (g) = volume (cm³) × density (g/cm³). This calculator assumes a solid part; a hollowed or low-infill print weighs proportionally less.

Material densities used for the weight estimate

The weight figure updates live when you change the material. The densities used are:

• PLA — 1.24 g/cm³
• ABS — 1.04 g/cm³
• PETG — 1.27 g/cm³
• Nylon (PA12) — 1.01 g/cm³
• TPU — 1.21 g/cm³
• Standard Resin — 1.10 g/cm³
• Aluminium (AlSi10Mg) — 2.67 g/cm³
• Stainless Steel — 7.9 g/cm³
• Titanium — 4.43 g/cm³

How the STL volume calculator works

1. Upload your STL or OBJ file using the dropzone above — it is read locally in your browser.
2. The engine welds coincident vertices and computes the real volume by summing signed tetrahedron volumes, plus surface area and the bounding box.
3. It checks whether the mesh is watertight and manifold; a closed mesh gives an exact volume, while an open mesh gives an approximate figure (repair it first for precision).
4. Choose a material to convert volume into an estimated printed weight, then use the figure to estimate print time, cost or shipping.

Everything runs entirely in your browser. No software to install, no upload to a server, and no account required.

Estimate print cost and time from volume

Once you know the volume and material weight, you can estimate what a part costs to print. Feed the volume into our 3D printing build-time & cost estimator, verify mesh quality with the STL analysis tool, or fix a broken model with the STL repair tool before measuring. When you are ready, get an instant 3D printing quote from iamRapid for FDM, SLA, SLS, MJF, PolyJet and metal printing across India.